Conventional wheelchairs are typically built around a chassis. Often the core of the chassis is a rectangular box-frame, which serves as the principal load-bearing structure of the wheelchair. Components, such as the wheels and seat, and accessories, such as footrests and armrests, can be mounted directly on the chassis.
The inventors have realised that although conventional wheelchairs can be adequate for their essential purpose of providing mobility for persons who are unable to walk (hereinafter referred to as invalids), they have drawbacks. For example, the chassis cannot be readily modified to accommodate invalids of extreme sizes. In addition, the chassis and the components and accessories mounted thereon often cannot be adjusted easily to suit the needs of an invalid, e.g. with particular postural requirements. This means that known wheelchairs may have to be separately modified to suit individual needs. Furthermore, conventional wheelchairs can on the whole be uncomfortable for the invalid and, where they are of the attendant push type, be inconvenient for the attendant to use. A significant drawback is a tendency towards chassis weakness that can make the conventional wheelchair unsuited to withstanding the forces exerted during a crash. This may be particularly important when an invalid is sat in the wheelchair when travelling in a motor vehicle.
European patent application EP 1 059 075A2 discloses a lightweight, variable position wheelchair. U.K. Patent application GB 2 040 237A discloses a wheelchair that is readily dismantled. German Utility Model DE 297 05 494U discloses a sports wheelchair.